SiPMs for cryogenic temperature

The DarkSide-20k collaboration is preparing to equip 20 m^2 of SiPMs working in liquid argon at 86 K for the direct search of WIMPs. The collaboration had to solve many technological aspects, such as the development of SiPM optimized for operation in liquid argon, the readout of large SiPM-based detectors, the reliable packaging of more than 200000 SiPMs using radiopure materials. The packaging solutions available for cryogenic applications and the performances of the newest cryogenic extended gain SiPMs from FBK will be discussed

Dust Formation By Failed Supernovae

We consider dust formation during the ejection of the hydrogen envelope of a red supergiant during a failed supernova (SN) creating a black hole. While the dense, slow moving ejecta are very efficient at forming dust, only the very last phases of the predicted visual transient will be obscured. The net grain production consists of ~0.01 solar masses of very large grains (10 to 1000 microns). This means that failed SNe could be the source of the very large extrasolar dust grains identified by Ulysses, Galileo and radar studies of meteoroid re-entry trails rather than their coming from an ejection process associated with protoplanetary or other disks.Comment: submitted to MNRA

Dust Formation in the Presence of Photons I: Evaporation Rates for Small Dust Grains

The temperature of newly forming dust is controlled by the radiation field. As dust forms around stars, stellar transients, quasars or supernovae, the grains must grow through a regime where they are stochastically heated by individual photons. Since evaporation rates increase exponentially with temperature while cooling times decrease only as a power law, the evaporation rates for these small grains are dominated by the temperature spikes. We calculate effective evaporation temperatures for a broad range of input spectra that are encapsulated in a series of simple interpolation formulae for both graphitic and silicate grains. These can be easily used to first determine if dust formation is possible and then to estimate the radius or time at which it commences for a broad range of radiation environments. With these additional physical effects, very small grains may form earlier than in standard models of AGB winds. Even for very high mass loss rates, the hottest stars that can form dust are G and F stars particularly in the case of silicate dusts. For hotter stars, the higher fluxes of ultraviolet photons prevent dust formation. Thus, episodic dust formation by OH/IR stars and LBVs is primarily driven by fluctuations in their apparent temperatures rather than changes in luminosity or mass loss rates.Comment: 13 pages, 10 figures, submitted to MNRA